Diesel engine testing apparatus



Dec. 9, 1947. D MORGAN 2,432,168

DIESEL ENGINE TESTING APPARATUS Filed March so, 1943 s Sheeis-Sheet 1 Lad/4 MONCTIWI ()FAIJ'EKA/ATQR DRIVE 57 SIMFT 61 Mm/nu mvzm R OHN D. l lRGAN W J P6 CY 6. L vrr'r 5 BY ATTORNEY Dec.- 1947- J. D. MORGAN ETAL ,432,168

DIESEL ENGINE TESTING APPARATUS INVENTORS a; JOHN D. MORGAN $4 new! a. LEVI'IT A 0 N Y Patented Dec. 9, 1947 I I UNITED STATES PATENT orncs DIESEL ENGINE TESTING APPARATUS John D. Morgan, South Orange, and Percy B. Levitt, Mllburn, N. J., assignors to Cities Service Oil Company, New York, N. Y., a corporation of Pennsylvania Application March 30, 1943, Serial No. 481,106

7 Claims. (01. 73-116) 1 This invention relates to apparatus for analyzimproved testing apparatus which may be syning the operation of and testing Diesel engines. chronized and phased with a two-cycle Diesel en- More particularly the invention relates to a gine and by which indicator cards may be made portable apparatus for analyzing the operation of and exhaust gases obtained and analyzed. two-cycle Diesel ngines, such for example as The apparatus of the present invention will be those directly connected to alternators. The apdescribed in connection with the accompanying paratus makes it possible to take indicator cards drawings forming a part of this'application and of any phase relation to crank pins, and furtherin which:

more includes a means for taking a gas sample Fig. l is a diagrammatic showing of the imfrom the engine cylinders at the commencement proved testing apparatus particularly illustratof exhaust and prior to the admixture of scaving the means for taking and analyzing exhaust enging air. The apparatus also includes means gases from a cylinder of a two-cycle Diesel enfor indicating directly the percentage of oxygen gine.

and combustibles present in the exhaust gas sam- Fig. 2 is a, top view of the instrument case ple taken. A very complete diagnosis of the en- (opened) for the testing apparatus illustrated in gine can be made with the information obtainable Figure 1 showing the portions of the apparatus by means of the apparatus of the present invenwhich are visible and attached portions, part of tion, to indicate the operation of the engine so which is in broken section. I that operation defects and characteristics may Fig. 3 is a vertical side elevational view of a be detectedand studied. portion of the instrument shown in Fig, 2.

The taking of a gas sample from a two-cycle Fig. 4 is a view of a portion of the driving Diesel engine is complicated by the fact that scavmechanism of the apparatus shown in Fig. 3,

enging air is admitted to the cylinder soon after lOOking from below, with parts broken away. the exhaust commences. Therefore, a sample Fig. 5 is an end view of the apparatus shown taken in the usual way would not be a true sample in Fig. 3 looking from the right, with parts brokenof the exhaust gas of the engine, but would be away. a

one diluted with scavenging air. The problem Fig. 6 is an enlarged vertical sectional view of taking the gas sample has been solved in the similar to that of Fig. 5 showing a portion of present instance by providing an apparatus which differential gear mechanism of the apparatus of includes a timing and valve mechanism for tak- Figs. 3, 4 and 5; and

ing the exhaust gas sample before it is mixed with Fig. 7 is an enlarged view partly in section of a scavenging air. portion ofa takeup device of the apparatus shown The timing mechanism of the apparatus of the in Figs. 2 and 3, taken on the line l-l of Fig. 3. present invention is also used for making. the The testing apparatus of the present invention indicator cards. In the past, it has been the 5 as shown diagrammatically in Fig, 1 includes a general practice to make indicator cards by taking synchronous motor l0 which for example operindicator motion from various parts of the enates at a speed of 1800 RF. M. The motor I) gine, such as the piston, cross-head, etc. Most has a shaft I2 which terminates at one end in a of the modern engines are enclosed so that such gear train I! by which the speedmay be reduced connections are not conveniently usable. Indicafor example to 360 R. P. M. on a connecting tor cards may be made by the use of the appashaft I6 which is the speed of the engine to be ratus of the present invention without having tested, The gear train l4 includes a gear-changany direct connection with the moving parts of ing arrangement by which any rotational speed the engine itself. from 120 to 360 R. P. M. may be obtained for The primary object of the present invention the connecting shaft I 6, by the choice of suitable is to provide an improved portable testing appagears. The shaft 16 terminates in a gearing arratus by which the operation of Diesel engines rangement shown generally at I'Lincluding adifmay be analyzed to thereby indicate ways of imferential gear which is adjustable by means of a proving the engine efliciency. hand knob and a gear wheel l8 riding on the A further object of the invention is to provide shaft l6. An outlet shaft I9 from the gear I! an improved testing apparatus particularly adaptterminates in a gear 20 which operates a shaft ed for the testing of-two-cycle Diesel engines. 2| having a crank disk 22 at its top and a contact A still further object of the inventionis to promaker 23 at its lower end. vide an improved apparatus for taking and ana- The motor shaft I2 has mounted thereon a lyzing the exhaust gas from the cylinders of twopair of collector rings 24, a, four-part commutator cycle Diesel engines. 26 and a pump 28, the pump being used for draw- Another object of the invention is to provide ing exhaust gases from the Diesel engine under an improved apparatus for operating engine intest and forcing them to the analyzer for the dedicators. termination of oxygen and combustibles.

Another object of the invention is to provide 00 Current, A. C., is supplied to the apparatus aasaie'a from a circuit directly or electrically connected to an alternator driven by the Diesel engine under ternating current approximately 450 volts is supplied from a transformer 32 to the collector rings 24 by lead lines 36. Any other voltage may be used which would be suitable for operating a stroboscopic lamp. The rectified current from a commutator 26 discharges through lead lines 31 to which is connected a twin electrode neon lamp 39, a 0.5 microfarad condenser 38 to keep an electrode of the lamp 39 glowing, and a crossover switch 40. This switch 40 connects to lead wires 4|, one ,of which includes the contact maker 23. The 'lead lines 4I also connect into a 120 microfarad tank condenser '42, a charging resistance 43 and a condenser 44 of about 30 microfarads. The lead wires 4I terminate in a switch 46 through which they may be connected through lead lines 48 with a stroboscopic lamp'50, or through lines 52 with an electro-magnet 54 for opening a gas sampler valve.

The lead lines 4| to the left of the cross-over switch 40 must have the plus and minus (polarity) characteristics indicated, whereas the current from the commutator 26 might produce a reverse polarity in the lead lines 31. .The cross-over switch is therefore used to provide the proper plus and minus current for the respective wires I.

The twin electrode neon lamp 39 is arranged in such a way that only the electrode connected to the plus lead wire 31 will glow, and the switch 40 is arranged so that all that is necessary to get current of proper polarity is to slide the switch in the direction ofthe glowing electrode, as indicated in Fig. 2 of the drawings.

The procedure and method of taking an exhaust gas sample from a cylinder of a Diesel en- Diesel engine cylinder 56 provided with a piston 58 which has a connecting rod 60 connected to a crank shaft 62 having thereon a flywheel 64. The crank shaft 62 is connected to and drives an alternator, not shown. The cylinder 56 is provided with the usual exhaust port or ports 68 which discharge into an exhaust gas manifold I6, and a scavenging air port or ports I2. The exhaust gas sample is taken directly in the exhaust port 68 by inserting a sampling tube I4 thereinto through any suitable opening such as a thermocouple hole in the exhaust gas manifold ID. The sampling tube I4 as'shown is arranged to take the direct blast of exhaust gas in the port 68 as soon as this port opens, The sampling tube I4 is furthermore provided with an outlet' open to the atmosphere at I6 and intermediately with a valve I8 (normally kept in closed .position by a spring),

opened automatically by the electro-magnet 54. The tube 14 ispreferably of uniform size to avoid gas pockets.

When it is desired to take a sample of the engine cylinder'exhaust, the switch 46 is closed to operate the electro-magnet 54, this operation be ing previously timed to occur an instant after the exhaust port .68-opens. The blast through the sampling tube has to dispel the residual gas through the outlet I6 before a true sample is obtainable. The point desired for the opening of the valve I8 is one corresponding to the lowest oxygen content or an instant after the port 68 is opened and before the port 12 is opened. The procedure for accurately adjusting the timing forthe taking of the gas sample is described more in detail hereinafter. A gas sample is taken by suction through the valve I8 by the pump 28 which is connected to the valve outlet by a tube 80 containing an enlarged surge chamber as shown to increase the gas flow. At the pump 28, the exhaust gas is discharged through two tubes 82 and 84 which lead respectively to separate analyzers for oxygen .gine is illustrated in Fig. 1 in which is shown a I haust.

and combustibles mounted in a housing 86. The detailed construction and operation of the analyzers is unnecessary since the preferred analyzer is shown for example in Patent No. 2,273,981, of which one of the present applicants is a joint patentee.

Each of the analyzers in the housing 86 is of the Wheatstone bridge type in which a catalytic electric heating element forms one leg of the bridge. Electricity for these catalytic heating elements is taken from the transformer 32 through lead wires 88 to a rectifier 98, one of the lead wires 88 being connected through parallel ballast lamps 92, such as amperites,- which are adapted to maintain a constant voltage in the circuit to the analyzer 86. Rectified D. C. current is supplied from the rectifier 90 through lead wires 94 and 96 to connector points 98 and I00 of the respective analyzer bridges in the housing 86, thelead wire 96 being connected through one of the amperites 92. The electric currents flowing through the Wheatstone bridges of the analyzer are controlled respectively by zero adjuster rheostats I02 and I04 which are connected by shunt circuits across the heatin legs of the bridges. The rheostat I04 is provided with a calibrating resistance I06.

In operating the analyzer apparatus for determining combustibles and excess oxygen in the engine exhaust gases, hydrogen for using up the free oxygen in the sample in line 82 is taken from a hydrogen cell I08 through a line H0 and thoroughly mixed with the engine exhaust gases in the line.82. The oxygen produced by the cell I68 is discharged through a pipe II I. Direct current for the hydrogen cell I08 is taken from the rectifier 90 in the manner indicated by the wiring. Outside air is not needed in line 84, because there is sufiicient excess free oxygen in the engine ex- The percentages of combustible and free oxygen in the engine exhaust gases may be read directly on millivoltmeters H2 and H4 respectively which are connected across the electric heating elements of the, respective Wheatstone bridges in the housing 86. The calibrations for the elements H2 and II 4 are shown in Fig. 2, in the opened position of the cover section of the instrument case. Fig. 2 also shows a number of the other elements of the apparatus of Fig. 1 and the other figures of the drawings, and the general arrangement of the apparatus in the instrument case.

The structure and method of mounting the motorized equipment described above is shown in substantial detail in Figs. 3 to '7. In Figs. 3 to 5, the motor In is shown as mounted on the underside of a horizontal panel H6 which is set in the main section of the instrument case. The gear mechanism referred to above is also mounted on the underside of the panel I I6 by a pair of spaced supports H8 and H9. The small gear wheel on the motor shaft I2 meshes with a large gear wheel I 20, from which a shaft I2I extends through the supports 'I I8 and I I9 and terminates in a gear wheel I22 fixed to the shaft, this wheel in turn meshing with a' gear wheel I24 which is mounted on a base I26 pivoted on the shaft I2I behind the gear wheel- I22. This base is provided with a' 5. v handle and a slot and locking bolt as shown in Fig.5. The gear wheel I24.also meshes with a holds the bearing pin removable gear wheel I28 mounted on the shaft I6. The-gear wheel I20 and the small wheel on the motor shaft gives a to 1 speed reduction. The size of the gear'wheels I22, I24 and I28 are selected so that any rotational speed from 120 to 360 R. P. M. may be obtained for the shaft I6.

These gear wheels are so arranged that the gear.

I28 may have and preferably does have the same number of teeth as, the number of poles in the alternator. This arangement facilitates the determination of the teeth and sizes for the gear wheels to give an R. P. M. for the shaft 2! equal to that of the R. P. M. of the Diesel engine crank shaft under test. The pivoted base I26 permits the use of a gear wheel I28 of any predetermined size, since the wheel I24 maybe swung toward or away from the shaft I6 to accommodate the selected gear wheel I28.

The shaft I6 is mounted in and extends through a, movable hub I32 (Fig. 4) which in turn is mounted in the support H9. terminates in the differential gear I1 which is mounted between the supports H8 and 1 I9 and which is keyed to the hub I32. The differential gear comprises a large driven bevel gear wheel fixed to the end of the shaft I6, which faces a similar gear wheel mounted on the shaft I9. The shaft I9 has a bearing in the support II8. As shown more particularly in Fig. 4, the-.diflerential gear also includes a pair ofspaced bevel pinions operating between the large bevel gear 6 and sprin'gf rm shown in Fig- 4 in a position tokeep the lead linev 4| open.

The spring arm and contact points-are mounted on a base I62 fastened to the lower edges of the supports H8 and II9,'above thewheel I60. The base I62 is capable of a limited rotational adjustment about the shaft 2I for changing the relative positions of the notch in the wheel I60 and the bearing pin on the spring arm, so that the 10 "contact occurs at a definite position for the crank disc 22.

The shaft 2I extends through th panel I I6 and the crank disc 22 is attached to its upper end.

, The rotation of this disc by the shaft 2I drives The shaft I6 v cross-head is also connected to a slide I10.which wheels, and mounted for rotation on a shaft I38, I

the ends of which extendinto-the differential gear casing. A gear wheel I40 mounted on the driven shaft I9 outside the support H8 and in a gear box, meshes with a gear wheel I42 on the shaft 2I for angle drive, these gears being arranged to give a ratio of 1 to 1 from the-shaft I9 to the shaft 2I. The diiferential gear I1 may be positioned as desired by rotating the hub I32 which is keyed to a gear wheel I8, which in turn is arranged for angle drive by a worm geared shaft I46 as shown more in detail in Figs. 5 and'6.

The position of the differential gear I1 is important in the operation of the apparatus because through this mechanism the circuit maker'23 may be synchronized with the Diesel engine under test, and the timing adjusted for the opening of the valve 18. The differential gear may be rotated through 360 by means of the shaft I46 which extends through'the panel H6 and terminates in a knurled dial head or hand knob I49 having a calibrated scale I50. The dial head I48 may be set and locked in any desired position by means of a knurled nut I 52. The dial head I48 is set above a panel I54 which is raised with respect to the panel II6 over the right end of the panel II 6 as shown in Figs. 2 and 3. The shaft I46 is also geared through a gear train I56 mounted between the panels H6 and I 54, to a dial I68 mounted above the panel I54 and calibrated in degrees. The dials I50 and I58 are rotated with respect to zero points indicatedon the panel I54 (Fig. 2). The rotation of the dial I58 one complete revolution, by hand knob I48, also rotates crank ,disc 22 one complete revolution, if the shaft I6 is not moved.

The contact maker .23 is ass ciated with the movable slide member I80 to which the sheave reciprocates in a guide I12 mounted at the top of the panel I I6, as shown in detail in Fig. 2 of the drawings. The crank disc 22 is provided with i I a mark "I which serves as a reference point to be matched with a mark I13 on the panel II6.

When these marks match, the slide I10 is at top dead-center, corresponding to the same point in the engine piston cycle.

An indicator cord I14 is attached directly to the cross-head I66 and taken around a sheave I16 on a take-up device including a pair of.

guides I18 (one of which includes a rack), a

I16 is attached, and to which is also attached a pinion, operable by a spring tensioned hand knob I82. The cord after passing around the sheave I16 then passes through a sheaved fair lead I84 from which it may extend to an indicator drum I86 (Fig. ,3) .of whatever engine indicator is being used. The drum I86 may be any drum and the indicator cord thereon to the desired position, this adjustment being made by operating the hand wheel I82 to move the slide I in th desired direction from the cross-head I66. With the indicator cord connected to the indicator drum and the apparatus in operation; it will be apparent that the-drum I86 will be os-' cillated in synchronism with the motion of the,

engine piston of the engine cylinder under test.

The Diesel testing apparatus ofthe present invention is very compact and readily taken to lower endof the shaft 2| (Figs. 1,- 3 to 5). and

comprises ,a-plain wheel I 60 having a notchin itscircumference which permits the closing of a. contacting one of the lead wires, 4 I,-with every revolution of, the wheel. The wheel .I60 normally the Diesel generator plants to carry out the tests, since the case shown in Fig. 2. in which the apparatus is mounted, is only as large as a medium sized suit case. To begin with, the instrument is" plugged into a .110 volt A..C. current supply made by-the alternator connected to the the rectified current from the commutator 26 7.6 lights'one side of, neon lamp. mounted under the openings Ill.(1'ig. 2), and the switch "is shifted in -the direction of whichever light is showing. Current of proper polarity is necesacsaioa for determination of their horsepower and. other characteristics. The improved apparatus is used with present indicators having the usual pressary to operate the lamp 5t and the electromagnet II.

The instrument is further adjusted or phased with any desired point in the engine piston cycle, as for example, top dead-center of the pisresult. The taking of data for the various cylinders and for different positions of the piston of each cylinder is greatly facilitated by setting the dial I58 at zero when the marks III and I13 are opposite.

leasing the locking knob I52 and rotating the dials I50 and I58 without rotating shaft I. The

This is accompished by redetailed structure shown in Fig. 6 is provided to permit the release of the dials from the shaft I for setting, and the locking of them to the shaft by means of the locking knob I52 which forces the dial knob I48 and connecting sleeve and small gear against a shoulder on the shaft I48 immediately above the panel I I6. Now if the firing order of the engine cylinders is known, top dead-center for the piston of any cylinder can be read off the positioning dial since of course the crank shaft angles of any particular engine are known. The taking of indicator diagrams for all of the engine pistons may be accomplished merely by setting the dial to the desired position for each cylinder. The phase relationship can be changed so that an indicator diagram can also be taken 90 ahead or after the crank pin (advance or retard), or at any other phase disthrowing the switch 46 to operate the valve I8,

so that the combustion gas sample is taken and conducted to the analyzer 86. The valve I8 is a very quick-acting valve and opens and closes in approximately /150 second. This rapidity of opening of the valve permits the sample to be taken through from 1 to 3 crankshaft degrees, depending upon'the speed of the engine. The timing of the valve is adjusted, as explained above, by the positioning knob I48, to occur at the precise moment the exhaust port opens, or slightly thereafter.

The improved testing instrument of the present invention provides an advantageous means by which indicator cards may betaken and the percentages of oxygen and combustibles in the two-cycle Diesel engine exhaust gases may be known, .and thus provide information suflicient for a very-complete diagnosis of its various individual cylinders, so that suitable measures may be taken for improving the engine's efllciency. Other piston-driven engines such as steam engines and other Diesel and internal combustion engines may beanalyzed by the apparatus .of the present invention by taking indicator cards sure connections to engine cylinders. The apparatus may be used for obtaining data which will aid in the adjustment of the main valves of such engines as well as injection valves'and the timing of the engine mechanism. Furthermore, the apparatus may be used as an aid in adjusting and equalizing the compressions of the different cylinders of the engine.

The synchronous motor I0 is powered by current produced by the alternator driven by the engine under test, unless some other means is pro-.

vided for keeping the testing apparatus in phase with the engine. The speed of the motor It may be the same as, or higher than, that of the engine under test, and. suitable gearing employed such as that described in the above examplefor obtaining the proper speed for the contact maker and crank disc. Instead of using the differential gear for phasing the crank disc and circuit maker with the engine under test, some other equivalent apparatus may be employed. Instead of phasing the apparatus with a point on the flywheel a point on another rotating part of the engine or alternator may be used. Other changes and. other means equivalent to various parts of the apparatus may be used in place of the specific parts described above, without departing from the invention.

While the testing apparatus of the present invention has been described in substantial detail, it will be apparent to those skilled in the art that various changes in structure and functioning of different parts may be made. Such changes however are contemplated as coming within the scope of this invention, as defined by the appended claims.

Having described the invention in its preferred form, what is claimed as new is:

1. An apparatus for analyzing the operation of a Diesel engine which comprises an exhaust gas sampler including an electro-magnetlcallyoperated valve through which the sample is drawn, anelectric motor operable at a substantially, higher speed than the Diesel engine being analyzed, a speed-reducing means connected with the shaft of said motor and to a rotary circuit maker, said speed-reducing means being arranged to provide a speed for the circuit maker equal to that of the speed of the Diesel engine being analyzed, an electric circuit for operating the electromagnet of said valve. said circuit maker being included in said electric circuit, means connected with said rotary circuit maker for providing a reciprocating motion for operating the drum of an engine indicator, and means for phasing said reciprocating means and said circuit maker with the piston motion of the engine cylinder under test whereby said electro-magnetically-operatcd valve may be opened at the desired point in the engine cylinder cycle to obtain an exhaust gas sample for analyses, and whereby an indicator diagram of the engine cylinder under test may be taken.

2 An apparatus for analyzing the operation of a Diesel engine, which comprises an exhaust gas sampler including an electro-magnetically-operated valve through which the sample is drawn, an electric motor operable at a constant speed, a speed-adjusting means connected with the shaft of said motor and to a rotary circuit maker. said speed-adjusting means being arranged to provide a speedfor the circuit maker the same as that of the speed of the Diesel engine to be analyzed, an electric circuit for.operating the electro-magnet of said valve including said circuit maker, means connected with said rotary circuit maker for providing a reciprocating motion for operating the drum of an engine indicator, and means for phasing said reciprocating means and said circuit maker with the piston motion of the engine cylinder under test whereby said electro-magnetically-operated valve opened at the desired point in the engine cylinder cycle to obtain an exhaust gas sample for analyses, and whereby an indicator diagram of the engine cylinder under test maybe taken.

3. An apparatus for analyzing the operation of a two-cycle Diesel engine connected to an alternator, which comprises an exhaust gas sampler for insertion into the exhaust port of the engine cylinder including an electro-magnetically-operated valve through which the sample is drawn, an electric motor operable at a-substantially constant speed on current from said alternator, a speed-adjusting means connected with the shaft of said motor and a rotary circuit maker, said speed-adjusting means being arranged to provide a speed for the circuit maker the same as that of the speed of the Diesel engine to be analyzed, an electric circuit for operating the electro-magnet of said valve including said circuit maker, means connected with said rotary circuit maker for providing a reciprocating motion for operating the drum of 'an engine indicator, and means for phasing said reciprocating means and said circuit maker with the piston motion .of the engine cylinder under test whereby said electro-magnetically-operated valve may be opened at the desired point in the engine cylinder cycle to obtain an exhaust gas sample for analyses, and whereby an indicator diagram of the engine cylinder under test may be taken.

4. An apparatus for analyzing the operation of a two-cycle Diesel engine, which comprises an exhaust gas sampler including an electro-magnetically-operated valve through which an exhaust gas sample is drawn from the exhaust gas port of the Diesel engine cylinder being analyzed, an electric motor operable at a substantially constant speed, a speed-adjusting gear train connected with the shaft of said motor and arranged to provide a speed which is the same as the speed of the engine under test, a shaft rotated by said gear train at the Diesel engine speed, said. shaft including an electric circuit maker in an electric circuit connected to said electro-magnet, said shaft also being connected to drive a reciprocating member in synchronism with the piston of may be the engine cylinder being tested, and means for I 10 tially constant speed, a speed-adjusting gea train connected with the shaft of said motor and arranged to provide a speed which is the same as the speed of the engine under test, a shaft rotated by said gear train at the Diesel engine speed, an electric circuit maker insaid electric circuit operated from said shaft, said shaft also being operatively connected to drive a reciprocating member in synchronism with the piston of the engine cylinder being tested, and means including a differential gear for phasing said circuit maker and said reciprocating means with the engine cylinder under test.

6. An apparatus as defined by claim 5 in which hand operative means is provided for rotating said differential gear, and thereby rotating said shaft relative to said motor.

7. An apparatus for analyzing the operation of a two-cycle Diesel engine'connected to an alternator, which comprises an exhaust gas sampler including an electromagnetically-operated valve through which an exhaust gas sample is drawn from the exhaust gas port of the Diesel engine cylinder being analyzed, an electric circuit for the electro-magnet of said valve, an electric motor receiving current from said alternator operable at a substantially constant speed, means for supplying electric current to collector rings mounted on the shaft of said motor, a commu-. tator on said shaft receiving current from said collector rings, means for supplying current from said commutator to-said circuit for said electromagnet, a speed-adjusting ear train connected with the shaft of said motor and with a driven shaft andarranged to provide a speed for said driven shaft which is the same as the speed of the engine under test, an electric circuit maker in said electric circuit operated by said driven shaft, said shaft also being operatively connected to drive a reciprocating member in synchronism with the piston of the .engine cylinder being tested, means forphasing said driven shaft with the engine cylinder under test, means for analyzing the exhaust gas from the engine cylinder for its content of free-oxygen and combustibles, a stroboscopic lamp for checking the timing of said driven shaft against that of the engine piston of the cylinder under test, and means for supplying electric current from said electric circuit to said stroboscopic lamp.

JOHN D. MORGAN. PERCY B. LEVITT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,781,013 Jacklin et a1 Nov. 11, 1930 2,077,538 Wait Apr. 20, 1937 2,192,863 Hetzel et a1. Mar. 5. 1940 2,236,422 Boley Mar. 25, 1941 1,890,601 Cox Dec. 13, 1932 2259,615 Chappeii Oct. 21, 1941' 2,261,655 Lowe Nov. 4, 1941 

